The invention relates to polymerizable preparations based on epoxides that contain silicon, and to their use.
In polymerizable dental compositions use has to date been made predominantly of methacrylate monomers and acrylate monomers. Particular attention is deserved by the 2,2-bis[4,1-phenyleneoxy(2-hydroxy-3,1-propane-diyl)methacrylate]-propylidene (bis-GMA) described by Bowen (U.S. Pat. No. 3,066,112). Mixtures of this methacrylate with triethylene glycol dimethacrylate are still used even today as a monomer matrix for dental plastic direct filling materials. Methacrylic derivatives of the diformylated bis(hydroxymethyl)tricyclo[5.2.1.02.6]-decane are also established as monomers for dental composites (W. Gruber et al., DE-A-27 14 538; W. Schmitt et al., DE-C-28 16 823; J. Reiners et al., EP-A-0 261 520). A great disadvantage of the known polymerizable dental compositions is the polymerization shrinkage, which in the case of filling material applications may, for example, give rise to secondary caries as a result of the formation of gaps at the edges. Furthermore, in the case of acrylate-based dental compositions, the inhibition polymerization by oxygen leads to the formation of what is known as a greasy layer, which in the case of fillings, for example, is unwanted and may even be harmful.
Despite the extensive experience which exists with epoxides and cycloaliphatic epoxides (U.S. Pat. No. 2,716,123, U.S. Pat. No. 2,750,395, U.S. Pat. No. 2,863,881, U.S. Pat. No. 3,187,018), such monomers and cationically polymerizable compositions formulated from them, having the properties needed for dental applications, have not become commercially available at any point in time.
The preparation of bifunctional cycloaliphatic epoxides has already been known for a good deal of time (U.S. Pat. No. 2,750,395, U.S. Pat. No. 900,506, U.S. Pat. No. 907,149, U.S. Pat. No. 2,745,847, U.S. Pat. No. 2,853,499, U.S. Pat. No. 3,187,018, U.S. Pat. No. 2,863,881, U.S. Pat. No. 2,853,498). Silicon-containing cycloaliphatic epoxides for producing three-dimensional objects by means of stereolithography were described by Crivello et al. in various publications (WO 96/30182, EP-A-0 449 027; J. Polym. Sci., Part A: Polym. Chem. 28 (1990) 479, ibid. 31 (1993) 2563; ibid. 31 (1993) 2729; ibid. 31 (1993) 3109; ibid. 31 (1993) 3121; ibid. 33 (1995) 2463).
The known cycloaliphatic epoxides essentially comprise low molecular weight monomers which, although possessing reduced polymerization shrinkage (DE-A-4 340 949), fail to meet the requirements imposed on materials for dental applications, owing to their toxicological properties.
Cationically curable epoxide compositions for dental applications are known, for example, from U.S. Pat. No. 5,556,896. That document describes epoxide compositions which have necessarily to contain spiroorthocarbonates as shrinkage compensating monomers.
Moreover, WO 95/30402 describes photopolymerizable compounds which comprise epoxide monomers. The compositions described therein are unsuitable for dental applications in the oral medium, owing to their high water absorption in the polymerized state.
The specifications WO 98/47046, WO 98/47047, and EP-A-0 897 710 describe epoxide compositions for dental applications that feature a novel initiator system but are based on conventional epoxide monomers. WO 98/22521 describes polymerizable compositions based on epoxides, intended for dental applications inter alia. Disadvantages of the epoxide compositions disclosed therein are the relatively high viscosity and the moderate reactivity of the monomer-containing compositions.
The epoxide compositions known to date, especially where monomers of low viscosity have been used, have exhibited high toxicity and/or mutagenicity and thereby restricting the possibilities for dental application.